Heretofore, there has been a gear shift device in which a shift drum that changes a speed change stage of a transmission according to a rotational position about an axis, is rotated by an actuator with a driving shaft thereof arranged parallel to this shift drum, to thereby change the speed change stage of the transmission (for example, refer to Patent Document 1).
On the other hand, employment of a worm gear mechanism has also been considered so that the driving shaft of the actuator becomes substantially orthogonal to the shift drum (for example, refer to Patent Document 2).    [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. H11-82734    [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. H09-324837